Referring now to FIG. 1, an exemplary data storage device 20 is shown. A buffer 24 stores data that is associated with the control of a hard disk drive. The buffer 24 may employ SDRAM or other types of low latency memory. A processor 26 performs processing that is related to the operation of the hard disk drive. A hard disk controller (HDC) 30 communicates with the buffer 24, the processor 26, a host 34, a spindle/voice coil motor (VCM) driver 36, and/or a read/write channel circuit 40.
During a write operation, the read/write channel circuit (or read channel circuit) 40 encodes the data to be written onto the storage medium. The read channel circuit 40 processes the signal for reliability and may include, for example error correction coding (ECC), run length limited coding (RLL), and the like. During read operations, the read channel circuit 40 converts an analog output from the medium to a digital signal. The converted signal is then detected and decoded by known techniques to recover the data written on the hard disk drive.
One or more hard drive platters 42 include a magnetic coating that stores magnetic fields. The platters 42 are rotated by a spindle motor that is schematically shown at 44. Generally the spindle motor 44 rotates the hard drive platter 42 at a fixed speed during the read/write operations. One or more read/write arms 46 move relative to the platters 42 to read and/or write data to/from the hard drive platters 42. The spindle/VCM driver 36 controls the spindle motor 44, which rotates the platter 42. The spindle/VCM driver 36 also generates control signals that position the read/write arm 46, for example using a voice coil actuator, a stepper motor or any other suitable actuator.
A read/write device 48 is located near a distal end of the read/write arm 46. The read/write device 48 includes a write element such as an inductor that generates a magnetic field. The read/write device 48 also includes a read element (such as a magneto-resistive (MR) sensor) that senses the magnetic fields on the platter 42. A preamplifier (preamp) circuit 50 amplifies analog read/write signals. When reading data, the preamp circuit 50 amplifies low level signals from the read element and outputs the amplified signal to the read channel circuit 40. While writing data, a write current that flows through the write element of the read/write device 48 is switched to produce a magnetic field having a positive polarity or negative polarity. The positive or negative polarity is stored by the hard drive platter 42 and is used to represent data. Data storage rates of these systems are proportional to a rate that the write driver circuit can change the direction of the write current through the write head.